1. Field of the Invention
The present invention relates to an optical switch and an optical waveguide apparatus used for switching of optical connection in an optical communication system.
2. Description of the Background Art
Referring to FIG. 26, an optical switch is provided for an optical waveguide 105 of a film polymer 102, i.e. a waveguide housing sheet 102, held between holding plates 103. Referring to FIG. 27, in an optical connection ON state (hereinafter simply referred to as ON state) in which a driving mechanism (push rod) 106 is not pushed at the crossing portion of the waveguide, waveguide housing sheet 102 keeps slit end surfaces 102a in contact with each other at a slit portion. Therefore, a core, i.e. waveguide 105, is also held in contact at the slit portion. Hence, the light arrived at the contact slit portion passed through the slit portion without its direction changed.
On the other hand, in an optical connection OFF state (hereinafter simply referred to as OFF state) in which push rod 106 is being pushed, push rod 106 pushes open slit end surfaces 102a from one side and separates them, as shown in FIG. 28, to expose the slit end surfaces to the air. Thus, the light propagated in the waveguide with a high refractive index cannot exit from one of the slit end surfaces, and changes the travelling direction approximately 90xc2x0 by total reflection due to the air in an air gap 109, and then keeps being propagated.
According to the above system, in FIG. 26, when the optical connection at the crossing portion of the waveguide is in the ON state, light inputs L1, L2 continuously pass through the portion where slit end surfaces 102a of a waveguide crossing portion 111 are in contact with each other. On the other hand, when the optical connection at the waveguide crossing portion is in the OFF state, input lights L1, L2 both totally reflects at the portion of the optical switch and change the travelling directions approximately 90xc2x0 to be output toward predetermined directions. As described above, the conventional optical switch is characterized in that the destination of light is switched by pushing/pulling one push rod 106.
Such an optical switch as described above has a problem when it switches from the OFF state to the ON state. That is, when the switch is switched from the OFF state, i.e. the state in which the push rod is pushed to totally reflect the light, to the ON state, i.e. the state where the light passes through, pulling back of the push rod only provides resilient force from the elasticity of the film polymer. This has caused a problem such that the contact between slit end surfaces 102a of film polymer 102 is insufficient, and sufficient contact of core 105 cannot be obtained.
It is an object of the present invention to provide an optical switch and an optical waveguide apparatus with excellent reliability and durability, which can perform stable and reliable ON/OFF operation of optical connection at a crossing portion of the waveguide.
According to the first aspect of the present invention, an optical switch is provided in an optical waveguide apparatus including waveguides through which light is propagated and a waveguide housing sheet enclosing the waveguides. The optical switch includes a slit portion slitting to traverse the waveguides; a driver (a driving mechanism) performing an driving action onto the slit portion; and a driver assistant member located to interpose the slit portion between the driver and the driver assistant member to assist the driver. The driver and the driver assistant member push open the slit portion and provide a gap between the waveguides, and brings the slit portion into contact to connect the waveguides.
By such an arrangement, deformation for restoring the connection, which conventionally had a problem in reliability, can be performed using a driver and a driver assistant member, for example, by loose constraint from both sides of the slit portion. This means that two members interposing the slit portion may be used to perform ON/OFF operation from both sides, instead of the conventional case where only one driver was used to perform ON/OFF operation from one side. This ensures connection of the slit portion to be restored and allows reliable switching from OFF state to ON state. Deformation to push open the slit portion by the driver has conventionally been reliable. Therefore, by enhancing the reliability of the restoring connection of the slit portion, the reliability of ON/OFF operation of optical connection can be enhanced. It is noted that the driver assistant member may be a member moving toward/from the slit portion in a reciprocating manner by a driving signal. However, even in such a case, the driver assistant member does not move in the same manner as that of the driver, but rather, moves to assist the driver. Furthermore, the waveguide housing sheet may be constituted by a film polymer or the like. Here, the term ON/OFF described above does not mean only whether the optical switch shuts off or passes the light which is input into the waveguide crossing portion. For example, the term ON/OFF may rather be used to define switching of the optical connection (output destination).
In the optical switch according to the first aspect of the present invention, the slit portion is preferably slit from one side of the waveguide housing sheet without the slit reaching the other side of the waveguide housing sheet.
By leaving a non-separated portion at the slit portion, the non-separated portion can be a reference at the time of restoring the connection of the slit portion, enhancing the reliability of restoration in restoring the end surfaces of the cores, i.e. the waveguides, to bring them again into contact with each other. Therefore, the reliability of the switching from OFF state to ON state can be enhanced.
In the optical switch according to the first aspect of the present invention, waveguides cross with one another inside of the waveguide housing sheet, and the slit portion may be arranged diagonally traversing the crossing portion when viewed two-dimensionally.
The arrangement ensures the light propagated in the waveguides to select its traveling direction, as to whether it continuously travels across the crossing portion in the same direction or it changes the direction and travels along a crossing waveguide.
In the optical switch according to the first aspect of the present invention, the driver moves forward to or backward from the slit portion in accordance with a driving signal, and the driver assistant member cooperates with the movement of the driver to act on the slit portion. The driver and the driver assistant member can push open the slit portion and can restore the slit portion to be back in contact.
This allows the use of a simple driving mechanism, and thus the optical switch and the optical waveguide apparatus can be provided at a low cost.
The optical switch according to the first aspect, at least one of the driver and the driver assistant member may include a member movable forward and backward along a direction approximately perpendicular to the waveguide housing sheet.
This allows ON/OFF operation by a short-distance movement, increasing the response speed of the optical switch.
In the optical switch according to the first aspect, the waveguide housing sheet is held by holding plates so as to support the waveguide housing sheet. Each of the holding plates preferably has an opening at a position corresponding to the slit portion.
This can ensure flatness of the waveguide housing sheet and can prevent a loss due to deformation of the waveguide. As a result, an optical waveguide apparatus with low-loss can be realized.
The optical switch according to the first aspect, at least one of the driver and the driver assistant member can be constituted by a piezoelectric element mechanically deformed in accordance with a voltage application.
A normal voltage application can induce high stress of hundreds of newtons, so that the piezoelectric element can be used for the optical switch of the present invention to perform reliable ON/OFF operation.
In the optical switch according to the first aspect, at least one of the driver and the driver assistant member may be constituted by an artificial muscle actuator.
The artificial muscle actuator has a deformation level of an animal muscle when a voltage is applied thereto. The artificial muscle may be made smaller to be on the order of tens of xcexcm in size of the section perpendicular to the direction of deformation, and thus may be used for a waveguide apparatus that is extremely small in size.
In the optical switch using the artificial muscle actuator according to the first aspect of the present invention, the artificial muscle actuator includes an apertured frame having an aperture at a position corresponding to the slit portion when viewed two-dimensionally, and an elastic film with electrodes (hereinafter also referred to as an electrode-attached elastic film) arranged between the apertured frame and the waveguide housing sheet. One artificial actuator is provided at the upper side of the waveguide housing sheet and another artificial actuator is provided at the lower side of the waveguide housing sheet so as to interpose the sheet in between, and the artificial actuator on either side may include an apertured spacer film, having an aperture at the same region as the aperture of the apertured frame, between the actuator and the waveguide housing sheet.
By this arrangement, the electrode-attached elastic film at a position corresponding to the aperture can be bulged by a voltage application to act on the slit portion. Furthermore, the side of the spacer film on the waveguide housing sheet may be determined as the side to which an air gap is formed open in OFF state. Such an arrangement allows smooth and highly reliable ON/OFF operation using the artificial muscle actuator together with the driver and the driver assistant member. Therefore, a very small driving mechanism may be constituted by a very simple arrangement.
In the optical switch according to the first aspect, the driver assistant member may be an elastic sheet arranged at the surface of the waveguide including the slit portion.
By arranging the elastic sheet as described above, a compressive force in the direction along which restoring connection of the slit portion is performed is applied from the elastic sheet extended due to the air gap opened in OFF state onto the waveguide housing sheet, ensuring ON state to be realized. By setting the elastic modulus of the elastic sheet to be a value indicating a rather rigid elasticity, more reliable switching to the ON state may be achieved. Metal, an organic material, a glass material or the like may be used for the elastic body. Thus, a simple mechanism may be employed to achieve reliable switching from OFF state to ON state.
In the optical switch according to the first aspect, a convex protrusion protruded toward the slit portion may be attached at a position corresponding to the slit portion of the elastic sheet.
This arrangement allows a resilience stronger than that in the case without the convex protrusion to act on the slit portion. As a result, the reliability of switching from OFF state to ON state can be enhanced. Furthermore, the OFF state may take two positions such as (a) a position where a gap is opened at the protrusion side of the waveguide housing sheet and (b) a position where a gap is opened at the driver side of the waveguide housing sheet. This results in enhancement of the degree of freedom of the design for the OFF position.
In the optical switch according to the first aspect, the driver assistant member may be a spring applying stress onto the waveguide housing sheet.
Using such an arrangement, an optical switch with enhanced reliability of ON/OFF operation can be obtained by a very simple mechanism. Moreover, the OFF state may take two positions such as (a) a position where a gap is opened at the spring side of the waveguide housing sheet, and (b) a position where a gap is opened at the driver side of the waveguide housing sheet. As a result, the degree of freedom of the design for the OFF position can be enhanced. It is noted that the spring may be of any form, e.g. a form of a helical spring or a plate spring.
The optical switch according to the first aspect further includes a protrusion-attached substrate held between the waveguide housing sheet and the holding plate, on which a state-holding protrusion is arranged that maintains the state of protruding to the surface side or to the back side, at a position corresponding to the slit portion.
This arrangement allows the ON/OFF state to be held without the driver driving, after switching of ON/OFF is performed. Thus, lower power consumption can be realized.
In the optical switch according to the first aspect, the driver and the driver assistant member touch the waveguide housing sheet on one side of the slit portion, when viewed two-dimensionally, to push open the slit portion and to restore connection, so as not to deform the waveguide housing sheet on the other side.
This arrangement can prevent bending deformation at the waveguide through which light passes, for example, in the OFF state, generating no excessive loss associated with deformation of a waveguide. Thus, an optical switch with a low loss can be realized compared to the configuration in which light passes through a deforming waveguide.
In the optical switch according to the first aspect, an end of the holding plate holding the waveguide housing sheet may be chamfered at an opening portion of the holding plate.
This arrangement can alleviate the stress generated at a root portion when the driver is arranged on each of the upper and lower sides of the waveguide housing sheet to warp the waveguide housing sheet, and therefore fatigue of the waveguide housing sheet can be prevented.
According to the second aspect of the present invention, an optical switch is provided in an optical waveguide apparatus including waveguides through which light is propagated, a waveguide housing sheet containing the waveguides, and a support-holding plate supporting and holding the waveguide housing sheet. The optical switch includes a gap dividing and separating the waveguides and the waveguide housing sheet; and a driver arranged to interpose the support-holding plate and the gap, and moving toward the gap to hold the separated waveguide housing sheets on both sides of the gap between the driver and the support-holding plate to deform the sheets to connect the gap, and also moving backward from the connected gap to restore the gap.
This arrangement allows an optical switch to be formed, which performs highly reliable ON/OFF operation while the driving mechanism is reduced to half. It is noted that the gap width may preferably be a width allowing the gap to be connected in close contact by deformation within the range of elasticity of the waveguide housing sheet.
In the optical switch according to the second aspect, waveguides cross with one another inside of the waveguide housing sheet, and the gap may be arranged to diagonally traverse a crossing portion, when viewed two-dimensionally.
By this arrangement, the light propagated through the waveguide can continuously travel without its direction changed, when the gap is deformed to be connected at the crossing portion. On the other hand, when the gap is restored, the light can change its direction to travel along a crossing waveguide. As a result, a traveling direction can reliably be selected by operating the optical switch.
In the optical switch according to the second aspect of the present invention, an elastic sheet elastically deformable compared to the waveguide housing sheet is arranged between the waveguide housing sheet and the support-holding plate, and the gap may continuously be provided to the elastic sheet.
The arrangement allows the gap to be filled without application of extremely large force onto the waveguide sheet. This eliminates the possibility of causing plastic deformation onto the waveguide housing sheet, and hence a highly reliable optical switch performing reliable ON/OFF operation may be provided.
The optical waveguide apparatus of the present invention may include any one of the optical switches described above at a crossing portion where waveguides cross with one another.
By such an arrangement, an optical waveguide apparatus having an optical switch with enhanced reliability of the ON/OFF operation and with excellent durability can be obtained. In the optical waveguide apparatus, an optical switch provided at the crossing portion may be used to select the direction of light.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.